1. Field of the Invention
The invention relates to a thin optical imaging module of a biometric apparatus, and more particularly to the thin optical imaging module that performs scanning upon the fingerprint and the vein so as to benefit the following verification, recognition or identification work.
2. Description of the Prior Art
To enhance the security level, assure the safety, and amend possible shortcomings in personal pin numbers, digital golden keys, built-in hardware golden keys of the smart chip and the like element for digital identification technology. Nowadays, more and more identity recognition and security systems have adopted or implemented with some kinds of biometric apparatuses. Among all these biometric apparatuses, the fingerprint identification device and the vein identification device are two of popular biometric apparatuses.
On the other hand, a dual-mode biometric module, though reliable, faces a major problem in software integration. In the art, relevant detectors are included to meet different objects to be detected. For example, in a fingerprint-and-vein dual-mode biometric module, one image sensor shall be included to perform and manage the vein image, while another image sensor with an optic prism shall be also included to handle the fingerprint image (or applying a capacitor-type fingerprint detector). The major reason to include two types of sensors is because the instinct imaging technology for the vein and the finger are different. For imaging the vein, an ultra-red light to penetrate the finger can be sufficient to capture the vein image in the finger. However, to capture the fingerprint image, the optical theory of total reflection upon an optic prism shall be utilized so as sufficient to increase the degree of recognition upon the ridges and the valleys on the fingerprint.
Basically, the optical paths for capturing the vein image and the fingerprint image are different. In addition, the arrangement of the conventional fingerprint prism is highly related to the increase of the module volume. Further, though the capacitor-type fingerprint sensor can be produced in a reduced volume, yet the distant client end would meet the following situations: (1) questionable reliability of the capacitor-type fingerprint sensor while is applied to face plural devices or systems, and (2) price hike upon the whole module due to the usage of the capacitor-type fingerprint sensors.
In a Taiwan patent application with a publication number 201413596 (TA 596, hereinafter), the applicant mentioned that a prior application “Biometric apparatus and method” can resolve the aforesaid shortcomings of the conventional dual-mode biometric modules. However, in TA 596, a conventional prism was still applied to provide two different optical paths for the dual-mode biometric module. For the conventional prism performed as a light-guide module has a larger and hard-to-be-reduced thickness, and also for the conventional prism would contribute one more reflection there inside, so the image would encounter a nonlinear deformation, thus unexpected. It is one of the incentives for the applicant to devote to introducing the following thin optical imaging module of a biometric apparatus in this disclosure.
According to the image-capturing module for the fingerprint and the vein currently in the marketplace, for example the NEC HS-100 the fingerprint optical imaging module, it usually applies two image sensors simultaneously to capture respectively one fingerprint image and one vein image. Through different image sensors with specific focusing ranges to capture and identify the fingerprint and the vein, the time spent on capturing and handling the images may be reduced, but the overall cost for the module would be increased substantially.
In another example, the M2SYS fingerprint optical imaging module (FUSE-ID), in order to provide an integrated system having an optical imaging module and a fingerprint module, the whole size of the system is high to 100 mm*120 mm*74 mm. The system has two image sensors for capturing the fingerprint image and the vein image, respectively, and the time for completing the image capturing is somehow extended.
Accordingly, a thin optical imaging module of a biometric apparatus is thus provided in this disclosure, in which a glass substrate has an optical prism film (prism sheet) attached thereon and a single image sensor, so that the required optical path as well as the volume can be reduced. Through the single image sensor, the fingerprint image and the vein image can be captured simultaneously in a single action. Upon such an arrangement, the volume for accommodating the prism module can be substantially reduced, the deformation of the optical path can be reduced to a minimum, and thus the distortion of the image can be improved. Further, the processing speed for the system to perform the recognition can thereby be increased.